This invention is directed to a process to thermally convert a heavy residual oil of low value to a solid fuel and a vapor stream which may be further combusted as a fuel for production of energy or process steam. More specifically, the invention relates to a heavy residual oil with high density, high sulfur content and high viscosity, such as which cannot be shipped or pipelined as-such. The means of thermal conversion uses a fluidized bed system whose fluidizing gas is produced by the fluid catalytic cracking (FCC) process.